Contact between a slider and the rotating disk surface it accesses is a key factor leading to reliability failures in hard disk drives. These contacts can occur during normal operations of the hard disk drive for any of several reasons, such as changes in environmental or atmospheric condition and/or external mechanical shocks which may include dropping a notebook computer or music player containing the hard disk drive.
Hard disk drive manufacturers have difficulty knowing when such contacts occur. Previously, two approaches existed for detecting contacts: the first relied on frequent measurement of the flying height clearance of the slider off the rotating disk surface. The second relied on monitoring the positional error of the slider when following a track on the disk surface, if it jumped suddenly, then contact could be surmised.
Both of these approaches have problems. The first approach was not economically feasible in mass produced hard disk drives because it was risky and tended to degrade performance. The second approach could only detect a strong, disruptive contact at certain head positions. It could not detect any contact. And its detection tended to lag behind the event, making it difficult to know exactly when contact occurred. Neither approach is acceptable.
An economical, non-disruptive approach is needed to monitoring the activity of a hard disk drive that accurately detects these contacts between a slider and the rotating disk surface it accesses, which can be field deployed in hard disk drives.